Types of System Modal Message Boxes

The information in this article applies to:

• Microsoft Windows Software Development Kit (SDK) version 3.1

SUMMARY

There are two kinds of system modal message boxes:

• Hard System Modal Message Box

  A hard system modal message box is the only window in the system that will receive messages.

• Soft System Modal Message Box

  All windows owned by a soft system modal message box's task will receive messages. No other window in the system will receive messages.

MORE INFORMATION

If a task wants to bring up a system modal message box and requires that messages be received by its other windows, a soft system modal message box must be used. For example, a task may require that WM_TIMER messages be received by a window it owns even while it displays a system modal message box. On the other hand, a hard system modal message box will prevent any other window in the system from receiving messages. A hard system modal message box is also appropriate in low memory situations because it uses very few system resources.

Both hard and soft system modal message boxes are created using MessageBox(). The MB_ICON* flags indicate the kind of system modal message box to be created.

A hard system modal message box can be created using MessageBox() and by including the following flags in the fuStyle parameter:

     MB_SYSTEMMODAL

(Other flags such as MB_OK, MB_OKCANCEL, and so forth can also be used. However do not use any other MB_ICON* flags).

A soft system modal message box can be created by including the following flags in the fuStyle parameter

   MB_SYSTEMODAL | MB_ICON*

(Other flags such as MB_OK, MB_OKCANCEL, and so forth can also be used. However do not use MB_ICONHAND or MB_ICONSTOP.)

Note that other tasks in the system do not receive any messages when a task puts up a hard or soft system modal message box.